Air-cleaning centrifugal-blower apparatus



Nov. 17, 1959 G. P. LESSMANN AIR-CLEANING CENTRIFUGAL-BLOWER APPARATUS Filed April 24, 1957 Fig. IA.

4 Sheets-Sheet 1 G. P. LESSMANN AIR-CLEANING CENTRIFUGAL-BLOWER APPARATUS Filed April 24, 1957 Nov. 17,1959

4 Sheets-Sheet 2 Nov. 17, 1959 s. P. LESSMANN 2,913,504

AIR-CLEANING CENTRIFUGAL-BLOWER APPARATUS Filed April 24. 1957 4 Sheets-Sheet 3 Fig.3.

' AIR-CLEANING CENTRIFUGAL-BLOWER APPARATUS Gerhard P. Lessmann, Forest Hills, Pa., assignor' to Westinghouse Electric Corporation, East Pittsburgh, Pa, a corporation of Pennsylvania Application April 24, 1957, Serial No. 654,916

3 Claims. (Cl. 310- 56) My invention relates to air-cleaning centrifugal blowers, and particularly their application to dynamo-electric machines which are used underneath railway cars, or in other places where the machines are operated in air which is quite dirty.

Heretofore in railway cars, both traction motors and motor-generator sets have been mounted under the floors of the cars, and have always been designed with ventilating arrangements based upon the concept that the extreme amount of dirt and other air-contamination dictated the type of ventilation. Such machines have been either relatively low in output, or relatively heavy for a given output. The motor-generator sets, which have heretofore been mounted underneath the car-floor, have been totally enclosed machines of the internal-externalventilation-type, in which the dirty air was blown over the outside of the machine-enclosure, while the internal air was circulated within the enclosure.

The traction-motors which have heretofore been mounted in the trucks of railway-cars, in places Where there has been very considerable air-contamination, have been either force-ventilated or self-ventilated. In the case of force-ventilated motors, clean air was obtained from a point considerably above the roadbeds, and was driven by a separate motor-driven blower, into duct-work which had to be provided underneath the car, to blow the clean ventilating air through the motors. This ductwork necessarily had to be arranged with flexible connections between the motor and the stationary air-ducts under the car, so as to allow free movement of the truck when going through curves. This system, while satisfactory from a ventilation-standpoint, has generally cost extra money and extra maintenance.

The traction-motors which are mounted in the trucks of railway-cars are practically always series commutatortype motors, which have such superior speed-torque characteristics as to have practically displaced all other types of traction-motors. When these truck-mounted commutator-type traction-motors have been self-ventilated, their ventilating fan or blower has always been disposed at the rear end of the armature; that is, at the end of the 'machine opposite to the commutator, so as not to interfere with free access to the commutator. Traction-motors are always reversible, so that they can be operated in either direction of rotation, to propel the car in either direction. Hence, it was necessary that the rear-endmounted blowers should be centrifugal blowers, because no other type of blower would blow air in the same direction for both directions of rotation. These centrifugal blowers always sucked air out of the motors, and threw olf the heated air into the outside atmosphere.

This method of self-ventilation has been subject to the very serious disadvantage that the air within the motor is at a negative pressure, or a partial vacuum, so that any moisture, dirt or other contamination which exists in the outside air will be sucked into the motor at the inlet-openings at the commutator end, or through any States Patent Patented Nov. 17, 1959 other cracks or openings in the motor-enclosure, unless special precautions are taken, which would again raise the cost of the motor. Filters, in general, are unsatisfactory, because they require too-frequent replacement. Airturns have some success, but they will not eliminate large amounts of dirt and contamination.

This is the state of the heretofore-known art to which my present invention is particularly directed.

The principal novel feature of my invention consists in the provision of a centrifugal blower which will first skim olf, centrifugally or peripherally, most of the dirt and contamination of the air which is being handled, thereby resulting in the wastage of perhaps 10% of the air which is moved by the blower. The rest of the bloweroutput is then delivered laterally, or in an axial direction, into the machine-enclosure, so that the centrifugal blower, now, for the first time in traction apparatus, blows the air, with a positive pressure, through the machine, rather than sucking the air out of the machine. As applied to motor-generator sets, this method of ventilation, in spite of its 10% air-wastage, makes it possible to increase the rating of a particular motor-generator set, from 2 kw., for example, to 3 kw. or more. As applied to railway traction-motors, my invention removes substantially all of the very great difiiculties which have heretofore been encountered in operating such motors in dirty atmospheres.

In applying my air-cleaning positive-pressure centrifugal blower to the rear end, which is the pinion or coupling end, of a series commutator-type traction-motor, it is extremely advantageous to also introduce a bafiie which causes the blower-air, which comes in at points near the outer periphery of the rear end of the motor, to first move downwardly, or radially inwardly, toward the shaft, and then underneath the baflle to move radially outward again, past the end-turns of the rotor-winding at that end of the machine.

This is of more importance than at first would seem to be apparent, because the rotor end-windings themselves act like a centrifugal blower, tending to move the air in a radially outward direction; that is, toward the periphery of the motor-housing. In the past, when centrifugal blowers have been used to suck air out of the motor, this centrifugal blowing-action of the rotor endwindings was bad enough, because the centrifugal fan sucked the air out of the motor from a point near the shaft, beneath the rotor end-windings, against the centrifugal action of the end-windings. In my new tractionmotor, in which the centrifugal blower is delivering the air into the motor-housing at a point near the outer periphery, the incoming air from the centrifugal fan or blowerif it were not for the added bafllewould be flowing radially inwardly, against the radially outwardly flowing air which was being moved by the centrifugal action of the rotor end-windings, so that the centrifugal fan or blower would have to be made large enough to overcome this opposing action of the end-windings-except for my addition of the bafiie.

However, with the baffle interposed between the blower and the end-windings, the air which comes from the blower flows in the same direction as, and merges with, the air-movement induced by the end-windings, thus obtaining an arrangement which might be called a two-stage blower. This arrangement provides ideal air-entry conditions in the motor, for the air coming from the main fan or blower, and it further provides a booster-action t0 the main fan, produced by the end-windings, for aiding in putting air through the motor. The result will be a decreased size of the main fan or centrifugal blower, with a resulting decrease in the horse-power which is required by the blower.

The importance of this reduction in the blower horsepower may not be immediately apparent to anyone who is not thoroughly familiar with the problems of railwaycar propulsion. Railway cars operate at variable speeds. The horse-power requirements of a fan or blower increase with the third power of the speed. Hence, at high car-speeds, the loss of horse-power in the blower, which has to be deducted from the available horse-power output of the motor, may be quite considerable. But it is at high speeds that the maximum horse-power output of the motor is the most urgently needed, for motor-acceleration at high speeds, because it is impossible, with any reasonable-sized motor, to obtain, at high speeds, more than a small fraction of the tractive effort which is obtained during starting conditions. Thus, at the high speeds where the horse-power requirements of the blower are very great, every increase in available horse-power will be reflected in a much-needed increase in the tractive effort of the vehicle, and hence, in its balance-speed or speed at which its tractive effort exactly matches the drag of the vehicle or level tangent track.

In the accompanying drawing, I have shown illustrative forms of embodiments of my invention. Figs. 1A and 1B together show the left and right-hand halves of the top half of a longitudinal sectional view through a motor-generator set embodying my invention. Fig. 2 is a fragmentary cross-sectional view of the blower, on a plane indicated by the line lIlI of Fig. 113. Fig. 3 is a partial longitudinal sectional view of the rear end of a traction motor, embodying my invention, the sectionplane being indicated by the line IIIIII of Fig. 4, Fig. 4 is a partial transverse cross-sectional view on a plane indicated by the line IVlV in Fig. 3. V

In Fig. 1A I show the generator-end, and in Fig. 113 I show the motor-end, of a motor-generator set such as is suitable for mounting underneath the car-floor (not shown) of a railway-vehicle. The generator 5 of Fig. 1A and the motor 6 of Fig. 1B are both shown as series direct-current machines, mounted back-to-back, having their rotor members carried by a common shaft 7, so that their commutators 8 and brush-rigging 9 are at opposite ends of the set.

11, and two end-walls 12 and 13 which carry bearings 14 in which the shaft 7 is journaled. The stationary housing-member llil has only two major air-openings; namely, an air-inlet opening or openings 15, which are located in a radially-outward part of one of the end-walls, such as the motor end-wall 13 in Fig. 1B, and an air-outlet opening or openings 16, which are located in a part of the housing-member it remote from the inlet-openings 15, as shown at the left-hand end of Fig. 1A.

The shaft 7 has a right-hand shaft-end 17 (Fig. 1B), which extends through the motor-end bearing 14, which is carried by the end-wall 13 which has the housing inlets 15. This shaft-end 17 thus extends to the outside of the housing-member 1i and it carries a bladesupporting member 18, which extends radially outwardly from said shaft-end. This blade-supporting member 18 has an axially-outer blade-supporting surface 19 of the rotating part of a centrifugal fan.

At a point which is radially out from the shaft-end 17, this blade-supporting radially-outer rotating surface 19 carries a plurality of centrifugal blower-blades 21 which are supported, at their radially-inner ends, from the outer surface of said blade-supporting member 18, in spaced relation to the shaft-end 17, as shown in Fig. 1B.

The blade-supporting member 18 has an outer peripheral part 22 which rotates in a closely spaced relation to a portion of the end-Wall 13 which is radially inside of the air-inlet openings 15. p i 7 V The right-hand end of the stationary housing It) has a peripheral-wall extension-portion 23 which is situated radially outwardly in a spaced relation with respect to the tially) This motor-generator set has a common stationary enclosing-housing 10 which has a peripheralwall blade-supporting member 18 and with respect to the blades 21, so that this wall-extension 23 constitutes a stationary housing-portion for the centrifugal blower. The axially outer end of the Wall-extension 23 terminates in a stationary shroud 24, which is shown in Fig. 1B as being situated in a closely spaced relation to the axiallyouter ends of the blade-assembly, whereby air isdrawn in, under said shroud, to the radially-inner edges of the blades 21.

The portion of the peripheral-wallexthsibh-pdrtidn 23 which is situated opposite to theradially-outer or peripheral edges of the blades 21 is provided with the relatively small air-discharging openings 25, which are so located, and so limited in size and number as to skim off a relatively small proportion of the total amount of air which is given off by said blades 21, so as to centrifugally remove practically all of the contamination, from the air which enters the blower. When some of the aircontaminating particles are elongated, as in railway applications, it is preferable for the air-skimming openings 25 to be elongated, in the form of slots, rather than being round; so as to give the elongated particles a better chance to flutter through, without bridging across an opening which is necessarily narrow in order to reduce the amount of skimmed-off air. Such slots, when used, may extend either axially or tangentially (circumferen- The drawing shows axially extending slots 25, but I am not limited to this conformation.

When the blower rotates always in the same direction of rotation, as in Fig. IE, it is sometimes preferable to dispose the slots in an axial direction and to supplement the action of these air-skimming slots 25, by means of a plurality of spaced, suitably inclined vane-portions 26, the inner ends of which are spaced from each other to provide the aforesaid slots 25, as shown in Fig. 2. This streamlines the concentratedly contaminated air which is skimmed off by the slots 25.

The annular space, between the peripheralwall-extension 23 and the radially-outer peripheral "part 22 of the rotating blade-supporting member 18, is thus situated so that the useful cleaned-air output of the blower has to move axially inwardly, through the housing-inlets 15 of the motor-generator set, into the stationary housing-member 10 of the machine. The ventilating-air of the machine is thus blown into the machine by an air-cleaning centrifugal blower, and this ventilating-air is discharged out of the outer end of the machine, through housingou'tlets .16 such as are shown in Fig. 1A.

lt is desirable that the'air-cleaning centrifugal'blower should be designed so as to prevent the accumulation of the air-contamination particles on any sharp edges which face the movement of the air-stream. When the contaminating air-particles are quite small, this is not much of a problem, but where the blower is to be used in a subway, as is true in an important field of application of my invention, the problem is made more diflicult by a large proportion of brake-shoe particles, and by a rather considerable quantity of lint-particles. Some of the lintparticles come from overcoats and other articles'of clothing, and are of considerable length, up to a sizable fraction of an inch in length, or even more,'and these particles have a way of bending over the advance-edges of any thin obstructions to the air-flow, whence they are not easily dislodged.

it is a desirable feature of my invention, therefore, insofar as it is feasible in all such cases, to give the inner edges of the vanes 26, or, in general, the approaches to the air-skimming openings 25, and'the inner'edgesof the centrifugal-blower blades 21, a radius of curvature which is more or less commensurate with the longest lint-particle which is generally to be expected, such as is shown at the curved edges 26 and 21', respectively, in Fig. '2, where the radius ofcurvature may be a quarter of an inch.

'With such a construction, any lint which impinges upon such a curved surface is able to slide smoothly ofi of it,

on one side or the other, as distinguished from hanging over a sharp edge from which it cannot readily be dislodged.

When my invention is applied to a traction-motor, as shown in Figs. 3 and 4, the same air-cleaning centrifugalblower construction may be used. Such motors, however, are reversible, so that the blower must also be reversible, and its blades 21A (Fig. 3) will generally, therefore, be radial, instead of being inclined as shown in Fig. 2; and the streamlining discharge-air vanes 26 of Fig. IE will generally have to be omitted. The enlarged radius of curvature of the edges of the slots 25 is also harder to achieve, without the use of vanes, so that it is usually necessary, in the case of reversible blowers, to be content with slots 25 which are formed with a much more moderate radius of curvature, such as may be provided by folding back the edges of the slots, as shown at 25A in Fig.

When my invention is being applied to a single motor, as distinguished from a motor-generator set, it is desirable, if that motor is a commutator motor, for the blower to be mounted on a shaft-extension 17A (Fig. 3) at the rear end of the machine; that is, the end opposite to the commutator-end. Thus, the blower 18-21A-23 in Fig. 3 is shown as being mounted on the spur-gear couplingmember 30 of the motor. This rear-end mounting of the blower, in Fig. 3, brings the stationary housing-endwall 13A, which is provided with the housing-inlets 15, into a fairly close axial spacing with respect to the rotor end-windings 31 of the motor, so as to involve the hazard of a rather strong air-disturbance, if precaustions are not taken to prevent the radially inward movement of the blower-air, which comes into the motor through the inlets 15, from being interfered with by the radially outward movement of air which is induced by the centrifugalblower action of the rotor end-windings 31.

To prevent this interference, it is an important feature of my invention to provide a bathe-member 32 (Fig. 3) which extends radially inwardly from the peripheral housing-wall 11, in the space between'said end-wall 13A which carries the inlets 15, and the rotor end-windings 31 at that end of the motor. This baffle-member has a bore 33 which has a diameter which is less than the diameter of the rotor member, so that the blowing action of the rotor member assists the blower-blades 21A in blowing clean air through the motor. In this way, I considerably reduce the horse-power requirements of the blower, thus making considerably more motor-horse-power available, particularly at high speeds, where such horse-power is urgently needed, as previously explained.

While I have described and illustrated only two diiferent forms and applications of my invention, I wish it understood that the invention, particularly in its broader aspects, is not limited to the illustrated details or to the illustrated specific forms of embodiment.

1 claim as my invention:

1. A blower assembly comprising a rotatable centrifugal blower having generally radial blades, and housing means for said blower, said housing means including a plurality of vane members disposed circumferentially around the blower and radially spaced therefrom to cause air discharged radially from the blower to change direction and flow axially, said vanes being spaced apart to form slots therebetween to permit a relatively small part of said air to be discharged radially through the slots.

2. A dynamoelectric machine having a stator member and a rotor member, said stator member including an end bracket having openings therethrough for the entrance of ventilating air, a centrifugal blower rotatable with the rotor member and disposed outside of said end bracket, and housing means for said blower, said housing means including a plurality of vane members disposed circumferentially around the blower and radially spaced therefrom to cause air discharged radially from the blower to change direction and flow axially through said openings in the end bracket, said vanes being spaced apart to form slots therebetween to permit a relatively small part of said air to be discharged radially through the slots.

3. A dynamoelectric machine having a stator member and a rotor member, said stator member including an end bracket having openings therethrough for the entrance of ventilating air, a centrifugal blower rotatable with the rotor member and disposed outside of said end bracket, and housing means for said blower, said housing means including a plurality of vane members disposed circumferentially around the blower and radially spaced therefrom to cause air discharged radially from the blower to change direction and flow axially through said openings in the end bracket, said vanes being spaced apart to form slots therebetween to permit a relatively small part of said air to be discharged radially through the slots, and an annular baflle disposed inside the end bracket adjacent said openings, said bafile having a central opening of smaller diameter than the rotor member.

Blair June 19, 1934 Clason June 19, 1934 

